Transmission-mounted vehicle speed sensors have been provided to sense the speed of a vehicle. Because exposed portions of such sensors typically contact the transmission fluid to permit the sensor to function as intended, and unexposed portions of the sensors can be damaged by contact with contaminated transmission fluid, it is important to establish a seal between the fluid and the unexposed portions or to filter out the contaminants in the fluid. For instance, metal particles in the transmission fluid, were the fluid to leak into a sensor housing that houses an electric coil (a typical sensor component), could be detrimental to the functioning of the coil by shorting it out.
As understood herein, an o-ring (a toroidal rubber or plastic ring) can be used to establish a fluid seal to prevent leakage of transmission fluid into the housing, but o-rings can fail, or be damaged, thereby losing their effectiveness. Moreover, incorporating an o-ring into a sensor entails an added part as well as an added manufacturing step, thus increasing the cost of the sensor. The present invention recognizes that it is possible to provide a sensor having a portion exposed to engine fluid while blocking contaminants in the fluid from contacting the coil, without requiring o-rings or separate sealing devices.